If you have had this calculator for some time it may be a hardware problem where there is a bit of graphite from the button on the board stopping it from receiving the input carefully clean if it comes apart or use contact cleaner.
If it is a multi function calculator try going through the modes and get to to RAD or check the second function priorities. If none of that works hard reboot by taking out the battery.
What's wrong with it? Not working at all? Did you spill anything on it? Did you open the calculator up to look inside? Did you try to clean the contacts yet?
Joshua Freeman さんによる